CN114406463A - Ultra-high-strength steel welding-following ultrasonic auxiliary laser welding system and method - Google Patents
Ultra-high-strength steel welding-following ultrasonic auxiliary laser welding system and method Download PDFInfo
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- CN114406463A CN114406463A CN202210181281.XA CN202210181281A CN114406463A CN 114406463 A CN114406463 A CN 114406463A CN 202210181281 A CN202210181281 A CN 202210181281A CN 114406463 A CN114406463 A CN 114406463A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/20—Bonding
- B23K26/21—Bonding by welding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/10—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating making use of vibrations, e.g. ultrasonic welding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/70—Auxiliary operations or equipment
- B23K26/702—Auxiliary equipment
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Abstract
The invention discloses an ultra-high strength steel welding-following ultrasonic-assisted laser welding system and method. The method adopts a front-contact ultrasonic application mode, the high-frequency vibration energy field of ultrasonic waves acts on a welding pool through a test plate to be welded, and the solidification and crystallization process of the welding seam is improved by utilizing a series of beneficial effects. And a tail cylinder of the ultrasonic generating device continuously provides pressing force for the ultrasonic amplitude transformer in the welding process. The invention adopts six-axis robot drive, can realize the welding of complex track and space position, does not change the original laser welding system, and has simple equipment composition. According to the invention, the ultrasonic energy field is introduced into the laser welding pool, so that the problems of cold cracks and softening and embrittlement of a heat affected zone which are easy to occur during welding of the ultrahigh-strength steel for spaceflight can be effectively inhibited, and the comprehensive performance of the joint is improved.
Description
Technical Field
The invention belongs to the technical field of efficient laser welding and manufacturing of aerospace structural parts, and particularly relates to an ultra-high strength steel welding-following ultrasonic auxiliary laser welding system and method.
Background
The ultra-high strength steel generally refers to steel with tensile strength of more than 1400MPa at room temperature and yield strength of more than 1200MPa, and is mainly used for rocket engine shells, engine jet pipes and booster at all stages. The 30Cr3 steel is a martensite low-alloy ultrahigh-strength steel which is independently developed by relevant units in China on the basis of summarizing the ultrahigh-strength steel at home and abroad, and is applied to manufacturing a shell of a power cabin section of a solid rocket by the characteristics of high strength, good toughness, excellent comprehensive performance and the like.
The 30Cr3 steel has high carbon content, more alloy elements and high quenching tendency, and is easy to have cold cracks and the softening and embrittlement problems of a heat affected zone during welding. At present, aiming at 30Cr3 ultrahigh-strength steel, domestic welding tests have fewer reports, and only vacuum electron beam welding and argon tungsten-arc welding are involved. However, as the size of the engine increases, the vacuum electron beam welding is limited by the size of the vacuum chamber, and the process flow is complex, which is not suitable for large-scale production and application. However, the argon tungsten-arc welding has the problems of prolonged production period and large welding deformation due to low welding efficiency, divergent arc energy and wide heat affected zone.
Laser welding is an efficient and precise welding method using a laser beam with extremely high energy density as a welding heat source. The welding method has the advantages of high energy density, high welding speed, large depth-to-width ratio, small heat affected zone, small welding deformation and the like, is easy to realize automation and engineering application, and has been widely applied in the fields of aerospace, electronics, automobile manufacturing, nuclear power and the like. Compared with vacuum electron beam welding, laser welding can get rid of the limitation of the size of a vacuum chamber, and efficient and high-quality welding can be realized in an atmospheric environment. Therefore, the laser welding is applied to manufacturing the 30Cr3 steel solid rocket engine shell, so that the cost can be obviously reduced, and the production efficiency can be improved. However, as the laser welding has high heating and cooling speeds, the temperature gradient is large when the welding seam is solidified, so that the crystal grains are large, the element distribution is uneven, the alloy elements are easy to form low-melting-point eutectic and segregate in the crystal boundary, the tendency of generating hot cracks is increased, and the mechanical performance of the welding joint is influenced to a certain extent. In addition, the 30Cr3 steel has high content of alloy elements, is easy to form oxides and nitrides with oxygen, nitrogen and the like in the air during welding, and the impurities are involved in the melt and are difficult to discharge to form slag inclusion. When the laser welding process parameters are improperly selected, the welding process becomes unstable, the welding joint easily has the defects of air holes, undercut and the like, and the actual application requirements in the aerospace precision manufacturing field are difficult to meet.
At present, methods for improving a metal solidification structure, reducing internal defects and improving mechanical properties through physical fields at home and abroad mainly comprise means of current, magnetic field, ultrasonic treatment and the like, and the methods are firstly applied to the traditional casting field and gradually developed into the metal melting and solidification field such as welding and the like. Ultrasonic assistance is a new technique that has emerged in recent years to improve the performance of welded structures in the field of welding. The high-frequency vibration energy field of the ultrasonic wave acts on the welding molten pool, can generate cavitation effect, acoustic current effect and mechanical effect, and has obvious influence on the solidification and crystallization process of the molten pool, thereby playing a certain role in inhibiting the defects. When cavitation bubbles generated in a molten pool by the cavitation effect of the ultrasonic waves collapse, the ultrasonic waves can break dendritic crystals growing at the front edge of a solidification interface, heterogeneous nucleation particles are added, and the transformation of a welding line solidification structure from coarse dendritic crystals to fine isometric crystals is promoted. The ultrasonic acoustic flow effect promotes the interlayer flow of liquid metal in the molten pool, can obviously improve the uniformity of a temperature field and element distribution, and is favorable for floating up and escaping of bubbles and impurities. The particle high-frequency micro-vibration caused by the ultrasonic field in the molten pool can generate additional heat effect, so that the solidification time of liquid metal at the edge of the molten pool is prolonged, the molten pool metal can be favorably spread to the edge of a welding seam, and the welding seam with uniform formation is finally obtained. In addition, the high-temperature area near the molten pool is easy to generate compression plastic deformation under the action of welding ultrasonic impact due to the reduction of yield strength, and is superposed with tensile plastic deformation generated in the welding thermal cycle process, so that the effects of reducing welding residual stress and deformation are achieved, and the fatigue performance of the joint is improved.
The invention patent CN101690991A discloses an ultrasonic-assisted vacuum electron beam welding method, which aims to solve the technical problem that aluminum and aluminum alloy, especially cast aluminum alloy are easy to generate cavity defects such as air holes, cold shut and the like in the vacuum electron beam welding process, and provides ultrasonic energy with certain frequency and amplitude applied in the vacuum electron beam welding process. However, the method adopts a fixed-point ultrasonic application mode, and the distance between an ultrasonic action position and a heat source is continuously changed in the welding process, so that the distribution of ultrasonic energy acting on a liquid molten pool is not uniform. When the size of the welding material is large, the effective ultrasonic power acting on the whole welding seam is low.
The invention patent CN102059453A discloses a non-contact ultrasonic-assisted laser welding method, which aims to solve the problems of easy generation of pores, thermal cracks, joint softening and the like in laser welding of metals such as titanium alloy, aluminum alloy and the like, and inhibits the defects by introducing ultrasonic waves into a molten pool. The ultrasonic tool head does not contact with the workpiece in the welding process in a non-contact ultrasonic applying mode, so that the omnibearing automatic flexible welding is conveniently realized. However, the ultrasound of this method must travel a certain distance in air or a protective atmosphere before being transmitted into the welding area, and significant reflected energy loss occurs at the surface of the workpiece, so that the ultrasound has a weak effective effect. Due to the attenuation effect of ultrasonic wave propagation, the method requires that the distance between the ultrasonic vibration head and the molten pool is short, and for metals with high reflectivity such as titanium, aluminum and the like, energy reflected by a laser heat source can damage the ultrasonic vibration head to a certain extent.
The invention patent CN111545902A discloses a servo ultrasonic vertical auxiliary laser swing welding device, which couples laser swing and vertical vibration caused by ultrasonic waves to realize three-dimensional track motion of laser beams, increase the stirring effect on a molten pool and inhibit the generation of defects such as air holes, cracks and the like in aluminum alloy laser welding. The device adopts the mount evenly fixed along the circumference of laser head with four supersound generating device, and supersound generating device can drive the laser head and carry out vertical vibration and to the molten bath conveying supersound of laser head below. However, the device introduces a large number of ultrasonic heads, changes the original laser welding device greatly, is provided with a high vibration amplitude of the ultrasonic amplitude transformer, and can bring adverse effects on the overall precision of the laser head when working for a long time. Because the laser head is connected with supersound generating device machinery, when the defocusing volume of change laser, need the clamping height of manual regulation every ultrasonic head for guaranteeing the effect of supersound, the operation is comparatively loaded down with trivial details. In addition, the device adopts a non-contact ultrasonic application mode, and the problem that the effective action effect of the ultrasonic is weak can also exist.
The invention patent CN105364326A discloses a method for laser-ultrasonic double-sided welding of magnesium alloy. Aiming at the problems of hydrogen holes, thermal cracks and coarsening of crystal grains which are easily generated in the laser welding process of the magnesium alloy, the ultrasonic wave is applied to the back surface of the welding seam and is positioned in the same vertical plane with the laser beam and the welding seam, and the welding is completed by the synchronous movement of the laser beam and the ultrasonic amplitude transformer. The specific embodiment verifies the beneficial effect of the method. However, the method requires the laser head on the front side and the ultrasonic amplitude transformer on the back side to move synchronously with the welding line, and the equipment composition and the operation flow are complicated. Meanwhile, the ultrasonic amplitude transformer is positioned at the back of the welding seam, so that the method is not suitable for welding the annular welding seam of the small-diameter cylinder and is difficult to flexibly apply to the welding seam at other spatial positions.
The invention patent CN107570872A discloses a method for assisting laser welding of heterogeneous materials by ultrasonic vibration. In order to eliminate the defects of an unfused area, secondary phase precipitation, uneven element distribution and the like in the laser welding process of the heterogeneous material, a follow-up contact type ultrasonic auxiliary application mode is provided, and the application of the follow-up contact type ultrasonic auxiliary application mode is not limited by the welding size. However, in the method, the close contact between the ultrasonic vibration head and the surface of the workpiece is realized by manually adjusting the descending distance of the positioning device, the designed descending distance is in the micron order, the requirement on the adjustment precision is high, and the adjustment difficulty is high. When the surface appearance of the workpiece has certain fluctuation, the rigid pressing contact quantity control mode can not respond in time, and the continuous contact between the ultrasonic vibration head and the workpiece and the stable output of the ultrasonic are difficult to ensure in the welding process.
Through the search and analysis of documents in the prior art, the current ultrasonic-assisted laser welding is mainly applied to the welding of aluminum, magnesium alloy and dissimilar metals, the ultrasonic application mode is mainly non-contact, and the ultrasonic introduction positions have obvious difference. Aiming at the welding of the ultra-high strength steel 30Cr3 for aerospace, only electron beam welding and argon tungsten-arc welding are involved at present, and no report and application of a welding-following ultrasonic-assisted laser welding method are provided. The power cabin section shell is an important welding assembly, and not only bears great longitudinal and transverse overload during working, but also bears the impact of high-speed airflow and the severe environment of high temperature and high pressure during gunpowder combustion, thereby providing high requirements on the quality, the mechanical property and the dimensional precision of a welding seam. Therefore, in order to achieve the shape control and control targets of aerospace 30Cr3 steel welding and improve production quality and efficiency, more advanced welding processes and methods need to be explored urgently.
Disclosure of Invention
Aiming at the defects and the blank of the prior art, the invention aims to provide a welding-following ultrasonic auxiliary laser welding system and method for ultrahigh-strength steel for a power cabin shell in the aerospace field. A series of beneficial effects generated by the propagation of ultrasonic waves in a molten pool are utilized to improve the solidification and crystallization process of the molten pool, and the effects of refining grains and inhibiting defects such as air holes and cracks are achieved. Meanwhile, the advantages of easy automation realization and high welding efficiency of laser welding are exerted, and the high-efficiency and high-quality welding of the ultrahigh-strength steel for spaceflight is realized.
In order to achieve the above object, the present invention provides an ultra-high strength steel welding-following ultrasonic-assisted laser welding system, which is characterized by comprising an optical fiber laser welding system, an ultrasonic generation system and a PLC control system, wherein:
the optical fiber laser welding system comprises an optical fiber laser power supply, a laser welding head and an industrial robot;
the fiber laser power supply emits laser beams;
the laser welding head is assembled at the tail end of the industrial robot and is connected with the ultrasonic generating system through a connecting clamp, and the laser welding head guides laser beams to perform reciprocating scanning motion in a plane parallel to a to-be-welded test plate;
the industrial robot controls the movement of the laser welding head and the ultrasonic generating system;
the ultrasonic generating system comprises an ultrasonic amplitude transformer, the relative position of the ultrasonic amplitude transformer and the laser welding head is fixed, and the end part of the ultrasonic amplitude transformer is contacted with the welding test plate;
the PLC control system controls the ultrasonic generating system, the action of the industrial robot and the laser beam.
Preferably, the ultrasound generating system further comprises an ultrasound power supply, an ultrasound transducer, a cylinder, a compressed air generating device and a solenoid valve, wherein:
the ultrasonic transducer converts an electric signal sent by an ultrasonic power supply into mechanical vibration of ultrasonic frequency by the ultrasonic transducer, and transmits the mechanical vibration into the welding test plate through the ultrasonic amplitude transformer;
the cylinder is connected with the compressed air generating device through a gas reducing valve and an electromagnetic valve;
the cylinder continuously provides pressing force for the ultrasonic amplitude transformer;
the gas pressure reducing valve changes the pressure of the compressed air entering the cylinder;
the electromagnetic valve is connected with the PLC control system.
Preferably, the oscillation scanning laser head is provided with a circulating water cooling device and is connected with a fiber laser power supply; the light emitting end of the oscillation scanning laser head is provided with a compressed air protection air knife.
Preferably, the connecting jig comprises a connecting rail and a cylindrical fixing jig, wherein:
the cylindrical fixing clamp is used for clamping the outer wall of an ultrasonic transducer of the ultrasonic generating system;
one end of the connecting guide rail is connected with the laser welding head through a bolt, and the other end of the connecting guide rail is rotatably connected with the cylindrical fixing clamp.
The welding method based on the ultra-high strength steel welding-following ultrasonic-assisted laser welding system provided by the invention comprises the following steps:
the method comprises the following steps: polishing with abrasive paper to remove an oxide film on the surface of the welding test plate until the surface of the welding test plate is exposed with metallic luster, wiping the butt joint edge and the surface to be welded, and removing oil stains on the surface;
step two: fixing the processed welding test plate on a welding tool fixture;
step three: adjusting the position and the posture of a laser welding head to focus a laser beam on the surface of a workpiece, wherein the focal point is positioned at a position to be welded; teaching a welding track, adjusting a connecting clamp and a rotating mechanism to enable an ultrasonic vibration head to be in contact with the surface of a welding test plate and form a certain included angle with the horizontal direction, and enabling the ultrasonic vibration head to bias a laser action point for a certain distance;
step four: setting laser welding parameters and ultrasonic generation parameters, starting compressed air connected with an air cylinder, regulating gas pressure by using a pressure reducing valve, and starting laser welding shielding gas;
step five: the PLC control system is used for starting a laser power supply and an ultrasonic power supply, an ultrasonic generator firstly generates ultrasonic waves to act on a welding test plate, a laser welding head emits laser after 3s, and meanwhile, the industrial robot walks according to a welding track taught in advance to start a welding process;
step six: and moving the industrial robot to the position of the welding termination point, closing the laser power supply, keeping ultrasonic vibration for 3s, closing the ultrasonic power supply, and sequentially closing the protective gas and the compressed air.
Preferably, in the first step, a 30Cr3 test plate is adopted, and the thickness of the 30Cr3 test plate is 2-4 mm.
Preferably, in the third step: the defocusing amount of the laser is-1 to +1 mm; adjusting the included angle between the laser and the vertical direction to be 5-10 degrees; the scanning frequency is 25 Hz-200 Hz, the scanning speed is 30 mm/s-60 mm/s, and the scanning amplitude is 0.5 mm-3 mm; the welding track teaching points comprise initial position points, welding starting points and welding ending points; defining that the X direction of the connecting clamp is parallel to the welding direction, the Y direction is vertical to the welding direction, and the Z direction is parallel to the normal direction of a to-be-welded test plate; the included angle between the ultrasonic vibration head and the horizontal direction is 40-60 degrees, the contact point is offset by 0-20 mm relative to the X direction of the laser action point, and the Y direction is offset by 0-30 mm.
Preferably, in step four: the laser welding power is 3400-4200W, the welding speed is 0.8-1.4 m/min, the type of the shielding gas is pure argon, and the shielding gas flow is 20L/min.
Preferably, in the fourth step, the ultrasonic generation parameters include ultrasonic frequency and amplitude gain, the amplitude range of the corresponding ultrasonic vibration head is 1-2 μm, and the pressure of compressed air in the cylinder is 0.2-0.4 MPa.
Preferably, the preferred frequency is 20kHz, and the preferred amplitude gain range is 10% to 20%.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention applies the high-frequency vibration energy field of ultrasonic waves to a welding pool, and improves the solidification and crystallization structure of the welding line by utilizing the cavitation effect, the acoustic flow effect and the mechanical effect of the welding pool. Ultrasonic assistance is applied in the welding process, so that the flow between liquid metal layers of a molten pool can be enhanced, the homogenization of a temperature field and element distribution and the upward floating escape of air holes and inclusions are promoted, and the grains of a weld structure are refined. The problems of cold cracks and softening and embrittlement of a heat affected zone which are easy to occur during welding of the ultrahigh-strength steel for spaceflight can be effectively inhibited, the comprehensive performance of the joint is improved, and the shape control and controllability target of welding of the shell of the power cabin section is realized. Meanwhile, compared with the welding method adopted by the steel at present, the laser welding method adopted by the invention has the advantages of high energy density, high welding speed, small welding deformation, narrow heat affected zone, easiness in automation realization, no limitation of the size of a vacuum chamber in welding under an atmospheric environment and the like.
2. The invention adopts a contact type ultrasonic application mode along with welding, compared with a non-contact type or fixed point contact ultrasonic application mode, the ultrasonic energy utilization rate is high, the effect of the ultrasonic on the whole welding line is more uniform, and the ultrasonic intervention can be effectively carried out on a large-scale welding structure.
3. The ultrasonic auxiliary device is introduced through the connecting clamp without changing the original laser welding system, and is applied to the front surface of the workpiece along with welding ultrasonic, so that the equipment is simple in composition and convenient to implement and control.
4. The control of the laser welding system and the ultrasonic generation system and the adjustment of the compressed air of the air cylinder are integrated in the robot operation panel through the main control unit, so that the integration degree is high, and the operation is convenient. And the welding robot is driven by a six-axis robot, so that the welding of complex tracks and space positions can be realized.
5. The tail part of the ultrasonic vibration head is additionally provided with the air cylinder, and the pressing force of the ultrasonic vibration head on the surface of the test board can be conveniently controlled by adjusting the air pressure of compressed air entering the air cylinder. In the follow-up welding process, even if the surface of the test plate is locally uneven, the vibration head can be ensured to be in close contact with the surface of the test plate, and the effective application of ultrasonic energy is ensured.
Drawings
Other features, objects and advantages of the present invention will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of the ultrasonic-assisted laser welding system and method for welding the ultra-high strength steel for spaceflight;
FIG. 2 is a schematic view of the attachment clamp of the present invention;
FIG. 3 is a schematic view of an ultrasonic generating apparatus of the present invention.
The figures show that: the ultrasonic welding device comprises a laser welding head, a connecting clamp, a supersonic generating device, a welding test plate, a cylindrical fixing clamp, a guide rail groove, a rotating mechanism, an ultrasonic amplitude transformer, an ultrasonic transducer and a tail cylinder, wherein the laser welding head is 1, the connecting clamp is 2, the ultrasonic generating device is 3, the welding test plate is 4, the cylindrical fixing clamp is 5, the guide rail groove is 6, the rotating mechanism is 7, the ultrasonic amplitude transformer is 8, the ultrasonic transducer is 9, and the tail cylinder is 10.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in detail below with reference to the accompanying drawings: the embodiment is implemented on the premise of the technical scheme of the invention, and a detailed implementation mode and a specific operation process are given. The embodiments described below are only a part of the embodiments of the present invention, and not all of them. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
As shown in figures 1 to 3, the ultra-high strength steel welding-following ultrasonic auxiliary laser welding system and method for aerospace provided by the invention comprises an optical fiber laser welding system, an ultrasonic generation system and a connecting clamp. The optical fiber laser welding system comprises an optical fiber laser power supply, a laser welding head, a cooling device, a shielding gas device, a six-axis industrial robot and a parameter setting terminal. The ultrasonic generating system comprises an ultrasonic power supply, an ultrasonic transducer, an ultrasonic amplitude transformer, an air cylinder, a compressed air reducing valve and an electromagnetic valve.
The laser welding head is assembled at the tail end of a 6 th shaft of the industrial robot and is connected with the ultrasonic generating device through a specially-made connecting clamp. The end part of the ultrasonic amplitude transformer is contacted with a welding test plate, the relative position of the ultrasonic amplitude transformer and a laser heat source is kept unchanged in the welding process, and the welding-following ultrasonic-assisted laser welding process is realized under the drive of a robot. The air cylinder at the tail part of the ultrasonic generating device is connected with the compressed air generating device, and continuously provides pressing force for the ultrasonic amplitude transformer in the welding process, so that the ultrasonic amplitude transformer is ensured to be in close contact with a welding test plate. The ultrasonic transducer is connected with the ultrasonic power supply, and an electric signal sent by the ultrasonic power supply is converted into mechanical vibration of ultrasonic frequency by the ultrasonic transducer and is transmitted into the welding test plate through the ultrasonic amplitude transformer. The ultrasonic power supply, the laser power supply, the robot action and the opening and closing operations of the tail cylinder of the ultrasonic generator are integrated in the robot operation panel by the PLC master control device.
The laser welding head is provided with a circulating water cooling device which is connected with an optical fiber laser power supply, and the light emitting end of the laser welding head is provided with a compressed air protection air knife to prevent splashing generated in the welding process from damaging a laser light path.
The robot is a universal industrial robot with 6 degrees of freedom, and can drive a laser head and an ultrasonic auxiliary device to realize welding of complex tracks and spatial positions.
One end of the connecting clamp is connected with the laser head through a bolt, and the other end of the connecting clamp is connected with the outer wall of the ultrasonic transducer through a cylindrical fixing clamp. The device can realize the adjustment of the offset distance of the ultrasonic vibration head in three directions relative to the welding test board X, Y, Z and also can realize the adjustment of the incident angle of the ultrasonic vibration head. With 3 translational degrees of freedom and 1 rotational degree of freedom. In order to reduce the whole weight of the structure, the connecting clamp is made of aluminum alloy.
In the ultrasonic generating device, in order to lighten the structure and ensure the effective application of ultrasonic, the ultrasonic vibration head is made of titanium alloy, and the tail cylinder is made of aluminum alloy. In order to ensure the structural rigidity, the outer wall of the transducer, which is in contact with the connecting clamp, is made of Q235 steel.
And the tail cylinder of the ultrasonic generating device is connected with the compressed air generating device through a gas reducing valve and an electromagnetic valve. The gas pressure reducing valve is used for changing the pressure of compressed air entering the air cylinder, and then the ultrasonic vibration head is used for adjusting the pressing force of the surface of the test board. The electromagnetic valve is used for being connected with the PLC master control device to realize the integrated control of opening and closing of the air cylinder.
The invention also provides an ultrasonic-assisted laser welding system and method for the ultrahigh-strength steel for spaceflight, wherein the method comprises the following steps:
the method comprises the following steps: and (3) polishing and removing the oxide film on the surface of the 30Cr3 test plate to be welded by using a grinding machine until the surface is exposed with metallic luster. And (3) carrying out secondary grinding on the surface of the test plate by using sand paper, and eliminating local surface fluctuation generated by grinding by using a grinding machine so as to ensure that the surface of the test plate is smooth and flat. And wiping the butt joint edge and the surface to be welded by using acetone to remove oil stains on the surface.
Step two: and fixing the processed plate to be welded on a welding tool fixture, wherein the butt joint gap is less than 10% of the plate thickness.
Step three: and adjusting the position and the posture of the laser head to focus the laser beam on the surface of the workpiece, wherein the focal point is positioned at the position to be welded. The welding trajectory is taught by a robot operation panel. And adjusting the Z-direction position of the connecting clamp and the rotating mechanism to enable the ultrasonic vibration head to be in contact with the surface of the test board and form a certain included angle with the horizontal direction, and then adjusting the X, Y-direction position to enable the ultrasonic vibration head to bias the laser action point for a certain distance.
Step four: and setting laser welding parameters and ultrasonic generation parameters, starting compressed air connected with the air cylinder, and regulating the gas pressure by using a pressure reducing valve. And starting laser welding shielding gas.
Step five: and starting a laser power supply and an ultrasonic power supply by using the robot integrated control system, firstly generating ultrasonic waves by an ultrasonic generator to act on a to-be-welded plate, then emitting laser by the laser after 3s, and simultaneously starting a welding process by the robot walking according to a welding track taught in advance.
Step six: and (4) moving the robot to the position of the welding termination point, closing the laser power supply, and closing the ultrasonic power supply after keeping ultrasonic vibration for 3 s. And closing the protective gas and the compressed air in sequence to finish the welding process.
In the first step: the thickness of the 30Cr3 test plate is 2-4 mm.
In the third step: the defocusing amount of the laser is-1 to +1 mm. In order to prevent the laser device from being damaged by the reflected laser on the surface of the test panel, the included angle between the laser and the vertical direction is adjusted to be 5-10 degrees. The welding track teaching points comprise an initial position point, a welding starting point and a welding ending point. And defining that the X direction of the connecting clamp is parallel to the welding direction, the Y direction is perpendicular to the welding direction, and the Z direction is parallel to the normal direction of a plate to be welded. The included angle between the ultrasonic vibration head and the horizontal direction is 40-60 degrees, the contact point is offset by 0-20 mm relative to the X direction of the laser action point, and the Y direction is offset by 0-30 mm.
In the fourth step: the laser welding power is 3400-4200W, the welding speed is 0.8-1.4 m/min, the type of the shielding gas is pure argon, and the shielding gas flow is 20L/min. The ultrasonic generation parameters comprise ultrasonic frequency and amplitude gain, the preferred frequency is 20kHz, the preferred amplitude gain range is 10% -20%, and the amplitude range of the corresponding ultrasonic vibration head is 1-2 mu m. The pressure of the compressed air in the cylinder is 0.2-0.4 MPa.
More specifically, the ultrasonic-assisted laser welding method for welding the ultrahigh-strength steel for aerospace along with welding according to the embodiment is implemented based on the following devices:
the welding-following ultrasonic-assisted laser welding device shown in FIG. 1 comprises three parts, namely an optical fiber laser welding system, an ultrasonic generating system and a connecting clamp. The laser welding head 1 is assembled at the end of the 6 th axis of the industrial robot and is connected with the ultrasonic generating device 3 through a special connecting clamp 2. The end part of the ultrasonic amplitude transformer is contacted with the welding test plate 4, and the relative position of the ultrasonic amplitude transformer and a laser heat source is kept unchanged in the welding process. And under the drive of the robot, the laser beam and the ultrasonic amplitude transformer synchronously move to complete welding.
The connecting clamp shown in fig. 2 has one end connected to the laser head by a bolt and the other end clamping the outer wall of the ultrasonic transducer by a cylindrical fixing clamp 5. The clamp is provided with a guide rail groove 6, the offset distance of the ultrasonic vibration head in three directions relative to the welding test plate X, Y, Z can be adjusted by matching with fastening screws in all directions, and the incident angle of the ultrasonic vibration head can be adjusted by the rotating mechanism 7. With 3 translational degrees of freedom and 1 rotational degree of freedom. The X direction of the connecting clamp is defined to be parallel to the welding direction, the Y direction is perpendicular to the welding direction, and the Z direction is parallel to the normal direction of a to-be-welded test plate.
The ultrasound generation system shown in fig. 3 comprises an ultrasound power supply, an integrated ultrasound horn 8, an ultrasound transducer 9 and a tail cylinder 10. The ultrasonic transducer is connected with the ultrasonic power supply, and an electric signal sent by the ultrasonic power supply is converted into mechanical vibration of ultrasonic frequency by the ultrasonic transducer and is transmitted into the welding test plate through the ultrasonic amplitude transformer. The air cylinder at the tail part of the ultrasonic generating device is connected with the compressed air generating device through a pressure reducing valve, and continuously provides pressing force for the ultrasonic amplitude transformer in the welding process. The pressure of the compressed air entering the air cylinder is adjusted by the pressure reducing valve, so that the ultrasonic vibration head can control the pressing force of the surface of the test board. When the surface appearance of the workpiece has local fluctuation, the cylinder can drive the ultrasonic vibration head to make an instant response, so that the close contact of the ultrasonic vibration head and the workpiece is ensured, and the effect similar to that of a gas spring is exerted.
The ultrasonic-assisted laser welding method for the welding-following ultrahigh-strength steel for spaceflight is carried out according to the following steps of:
the method comprises the following steps: and (3) polishing the aerospace power cabin shell with the thickness of 2.5mm by using an ultrahigh-strength 30Cr3 steel by using a grinding machine to remove the surface oxide film until the surface exposes metallic luster. And (3) carrying out secondary grinding on the surface of the test plate by using No. 600 abrasive paper to eliminate local surface fluctuation generated by grinding by using a grinding machine so as to ensure that the surface of the test plate is smooth and flat. And wiping the butt joint edge and the surface to be welded by using acetone to remove oil stains on the surface.
Step two: and fixing the processed board 4 to be welded on a welding tool fixture, wherein the butt joint gap is less than 10% of the board thickness.
Step three: the position and posture of the laser welding head 1 are adjusted so that the laser beam is focused on the surface of the workpiece, and the defocus amount is preferably 0. In order to prevent the reflected laser on the surface of the test board from damaging the laser, the included angle between the laser head and the vertical direction is adjusted to be 5 degrees. And teaching the welding track by using a robot operation panel, wherein the teaching points comprise an initial position point, a welding starting point and a welding ending point, and the initial position point is 50mm above the welding starting point. And adjusting a Z-direction displacement mechanism and a rotating mechanism of the connecting clamp 2 to enable the ultrasonic vibration head 8 to be in contact with the test plate to be welded and to form an angle of 45 degrees with the horizontal direction. The X-direction and Y-direction displacement mechanisms of the connecting clamp 2 are adjusted to enable the ultrasonic vibration head to be offset from the laser action point for a certain distance, wherein the X-direction is offset by 0mm in the embodiment, and the Y-direction is offset by 20 mm. The connecting line of the laser action point and the ultrasonic action point is vertical to the welding seam direction.
Step four: and setting laser welding parameters and ultrasonic generation parameters. The laser welding power in the present embodiment is preferably 4000W, and the welding speed is preferably 1.2 m/min. The shielding gas is pure argon, and the shielding gas flow is preferably 20L/min. The ultrasonic generation parameters include ultrasonic frequency and amplitude gain, and in the embodiment, the frequency is preferably 20kHz, and the amplitude gain is preferably 10%. The compressed air connected to the tail cylinder 10 is turned on and the pressure of the gas is adjusted to 0.2MPa by the pressure reducing valve.
Step five: the laser welding head 1 and the ultrasonic power supply are started by utilizing the robot integrated control system, firstly, ultrasonic waves generated by the ultrasonic generating device 3 act on a to-be-welded plate 4, the laser emits laser after 3s, and meanwhile, the robot walks according to a welding track taught in advance to start a welding process.
Step six: and (3) moving the robot to the position of the welding termination point, closing the laser welding head 1, keeping the ultrasonic generating device 3 working for 3s, and then closing the ultrasonic power supply. And closing the protective gas and the compressed air in sequence to finish the welding process.
In the embodiment, the high-frequency vibration energy field of the ultrasonic wave acts on the welding pool, and the solidification crystalline structure of the welding line is improved by utilizing a series of beneficial effects. Under the condition of not changing the original laser welding system, a contact type ultrasonic applying mode along with welding is adopted, the equipment composition is simple, and the ultrasonic energy utilization rate is high. Meanwhile, the advantages of high laser welding energy density, small welding deformation and narrow heat affected zone are exerted, cold cracks easily occurring during welding of the ultrahigh-strength steel for spaceflight and softening and embrittlement problems of the heat affected zone can be effectively inhibited, the comprehensive performance of the joint is improved, and the shape control and control target of welding of the power cabin shell is realized.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and the above description of the embodiments is only for the purpose of helping understanding the method of the present invention and the core idea thereof. Various changes or modifications may be made by those skilled in the art within the scope of the claims without affecting the spirit of the invention, and the scope of the claims should be construed to include all modifications and alterations. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (10)
1. The utility model provides an ultra-high strength steel is along with welding supplementary laser welding system of supersound, its characterized in that, includes optic fibre laser welding system, supersound emergence system and PLC control system, wherein:
the optical fiber laser welding system comprises an optical fiber laser power supply, a laser welding head and an industrial robot;
the fiber laser power supply emits laser beams;
the laser welding head is assembled at the tail end of the industrial robot and is connected with the ultrasonic generating system through a connecting clamp, and the laser welding head guides laser beams to perform reciprocating scanning motion in a plane parallel to a to-be-welded test plate;
the industrial robot controls the movement of the laser welding head and the ultrasonic generating system;
the ultrasonic generating system comprises an ultrasonic amplitude transformer, the relative position of the ultrasonic amplitude transformer and the laser welding head is fixed, and the end part of the ultrasonic amplitude transformer is contacted with the welding test plate;
the PLC control system controls the ultrasonic generating system, the action of the industrial robot and the laser beam.
2. The ultra-high strength steel welding-following ultrasonic auxiliary laser welding system according to claim 1, wherein the ultrasonic generating system further comprises an ultrasonic power supply, an ultrasonic transducer, a cylinder, a compressed air generating device and a solenoid valve, wherein:
the ultrasonic transducer converts an electric signal sent by an ultrasonic power supply into mechanical vibration of ultrasonic frequency by the ultrasonic transducer, and transmits the mechanical vibration into the welding test plate through the ultrasonic amplitude transformer;
the cylinder is connected with the compressed air generating device through a gas reducing valve and an electromagnetic valve;
the cylinder continuously provides pressing force for the ultrasonic amplitude transformer;
the gas pressure reducing valve changes the pressure of the compressed air entering the cylinder;
the electromagnetic valve is connected with the PLC control system.
3. The ultra-high strength steel welding-following ultrasonic auxiliary laser welding system of claim 1, wherein the oscillation scanning laser head is provided with a circulating water cooling device and is connected with a fiber laser power supply; the light emitting end of the oscillation scanning laser head is provided with a compressed air protection air knife.
4. The ultra-high strength steel weld-following ultrasonic-assisted laser welding system of claim 1, wherein the connecting fixture comprises a connecting rail and a cylindrical fixing fixture, wherein:
the cylindrical fixing clamp is used for clamping the outer wall of an ultrasonic transducer of the ultrasonic generating system;
one end of the connecting guide rail is connected with the laser welding head through a bolt, and the other end of the connecting guide rail is rotatably connected with the cylindrical fixing clamp.
5. A welding method based on the ultra-high strength steel welding-following ultrasonic auxiliary laser welding system of any one of claims 1 to 4, characterized by comprising the following steps:
the method comprises the following steps: polishing with abrasive paper to remove an oxide film on the surface of the welding test plate until the surface of the welding test plate is exposed with metallic luster, wiping the butt joint edge and the surface to be welded, and removing oil stains on the surface;
step two: fixing the processed welding test plate on a welding tool fixture;
step three: adjusting the position and the posture of a laser welding head to focus a laser beam on the surface of a workpiece, wherein the focal point is positioned at a position to be welded; teaching a welding track, adjusting a connecting clamp and a rotating mechanism to enable an ultrasonic vibration head to be in contact with the surface of a welding test plate and form a certain included angle with the horizontal direction, and enabling the ultrasonic vibration head to bias a laser action point for a certain distance;
step four: setting laser welding parameters and ultrasonic generation parameters, starting compressed air connected with an air cylinder, regulating gas pressure by using a pressure reducing valve, and starting laser welding shielding gas;
step five: the PLC control system is used for starting a laser power supply and an ultrasonic power supply, an ultrasonic generator firstly generates ultrasonic waves to act on a welding test plate, a laser welding head emits laser after 3s, and meanwhile, the industrial robot walks according to a welding track taught in advance to start a welding process;
step six: and moving the industrial robot to the position of the welding termination point, closing the laser power supply, keeping ultrasonic vibration for 3s, closing the ultrasonic power supply, and sequentially closing the protective gas and the compressed air.
6. The welding method of claim 5, wherein in the first step, a 30Cr3 test plate is used, and the thickness of the 30Cr3 test plate is 2-4 mm.
7. A welding method according to claim 5, characterized in that in step three: the defocusing amount of the laser is-1 to +1 mm; adjusting the included angle between the laser and the vertical direction to be 5-10 degrees; the scanning frequency is 25 Hz-200 Hz, the scanning speed is 30 mm/s-60 mm/s, and the scanning amplitude is 0.5 mm-3 mm; the welding track teaching points comprise initial position points, welding starting points and welding ending points; defining that the X direction of the connecting clamp is parallel to the welding direction, the Y direction is vertical to the welding direction, and the Z direction is parallel to the normal direction of a to-be-welded test plate; the included angle between the ultrasonic vibration head and the horizontal direction is 40-60 degrees, the contact point is offset by 0-20 mm relative to the X direction of the laser action point, and the Y direction is offset by 0-30 mm.
8. A welding method according to claim 5, characterized in that in step four: the laser welding power is 3400-4200W, the welding speed is 0.8-1.4 m/min, the type of the shielding gas is pure argon, and the shielding gas flow is 20L/min.
9. The welding method according to claim 5, wherein in the fourth step, the ultrasonic generation parameters comprise ultrasonic frequency and amplitude gain, the amplitude range of the corresponding ultrasonic vibration head is 1-2 μm, and the pressure of compressed air in the cylinder is 0.2-0.4 MPa.
10. A welding method according to claim 9, characterized in that said preferred frequency is 20kHz and the preferred amplitude gain range is 10-20%.
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